1. Field of the Invention
The present invention relates to a chlorinated vinyl chloride resin composition. In particular, the present invention relates to a chlorinated vinyl chloride resin composition suitable for the production of extruded pipes.
2. Prior Art
Shaped articles of chlorinated vinyl chloride resin compositions have characteristics such as high heat resistance and are used at relatively high temperatures at which conventional vinyl chloride resin compositions cannot be used due to thermal deformation. For example, the shaped articles of chlorinated vinyl chloride resin compositions are used in the form of a pipe for hot water by making use of the high thermal deformation temperature which is 20 to 40.degree. C. higher than that of the shaped articles of vinyl chloride resin compositions.
Furthermore, when pipes are produced, chlorinated vinyl chloride resins can be shaped with a conventional extruder for vinyl chloride resins. The use of such an extrusion method is one reason for that the chlorinated vinyl chloride resin can be widely used.
However, chlorinated vinyl chloride resins have a drawback that they have inferior thermal stability to vinyl chloride resins, and thus they tend to be burnt in a shaping process. For example, a chlorinated vinyl chloride resin is colored when it is extrusion molded to produce a pipe for hot water, or in some cases, it is burnt during extrusion molding. Thus, such a produced pipe may not be commercially sold.
In addition, when a chlorinated vinyl chloride resin is extruded in the form of a pipe for hot water, the die pressure and extrusion torque of an extruder increase, and the resin is burnt. To prevent burning, with a conventional extruder for vinyl chloride resins, the discharge amount of chlorinated vinyl chloride resins should be decreased in comparison with vinyl chloride resins to reduce the die pressure and extrusion torque. That is, when extruded pipes are produced from chlorinated vinyl chloride resins, the discharge amount of the resins is low, and thus the productivity of the pipes decreases.